5.0.1 panics on USB wireless device

Dear All:
My desktop is running a 5.0.1 AMD64 fresh installation. Generic kernel.
Upon connecting a Belkin USB Wireless key, the device is correctly
recognized and the rum0 node is created.
Issuing a:
# wpa_supplicant -B -i rum0 -c /etc/wpa_supplicant.conf
results, after 30-60 seconds in a complete hang of the machine.
The console shows a series of numbers, 7500 7499 7488 ... etc.
Machine becomes completely unresponsive and the only solution is a hard
power-off. I can reproduce it, but it takes 20 min of file system checks
on next reboot.
wpa_supplicant.conf:
network={
ssid="MyNetwork"
psk="password"
}
Am I doing something wrong??
Thank you very much in advance for your help!
Regards,
Davide